string buffer needs

[Asko Kauppi <asko.kauppi@...>]

Referring to the recent discussion on a need for string buffer (general 
data buffer, ranges et.al.) has anyone made a API-like list of how that 
should really work? I mean, we could do it 'by hand' with Lua, awful 
performance but the codeability aspects could be experimented with.

Here's a couple of funcs that I'd personally find a use for in the 
remake of Lumikki:


** Find with a range **

int, int [capture_str [,...]]= buffer.findfrom( text_str, start_int, 
pattern_str )

This is a variant of 'string.find()' with a starting place (probably, 
range?) within a string.  Allows me to look for HTML tags etc. within a 
huge all-in-one string, without creating an awful lot of intermediate 
substrings.

Current implementation:	using 'string.find' and 'string.sub'

	-----
	-- [start_int, stop_int [,capture ...]]= string.findfrom( str, 
start_int, pattern_str )
	--
	local function string_findfrom( str, start, pat )
	    --
    	local tbl= { string.find( string.sub(str,start), pat ) }

	    if not tbl[1] then
    	    return nil
	    else
    	    tbl[1]= tbl[1]+(start-1)
        	tbl[2]= tbl[2]+(start-1)
	        return unpack(tbl)
    	end
	end


** In-place appending **

void= buffer.append( text_str, ... )

Ability to modify a string 'in place', without creating new entries all 
over.  This is basically the same as "str ..=" (C-like in-place 
operator syntax) would be.

Usage: gathering strings together, big data.  Perhaps there's a table 
function for this, I'll see..  (yes, 'table.concat' but I still needed 
to craft a temporary table to collect the strings first)

Current implementation: str= str..whatever
                    or: table.concat()

Question:  does anyone know of the performance difference between 
'table.concat' and regular appending?